1. Field of the Invention
The present invention relates to a control valve, and more particularly to a control valve including a diaphragm serving as a pressure sensing member.
2. Description of the Related Art
Control valves having diaphragms as pressure sensing members, such as expansion valves installed in refrigeration cycles, have been widely used. For example, such an expansion valve is formed by an assembly of a body having a valve section formed therein and a power element. The power element is provided with a diaphragm that partitions the inside of a housing of the power element into a closed space and an open space. The closed space is filled with a gas for sensing pressure, and the open space communicates with the inside of the body. The diaphragm senses a pressure difference between the closed space and the open space, and is displaced thereby in an axial direction. A drive force caused by the pressure sensed by the diaphragm is transmitted to a valve element via a disc and a shaft, which regulates the opening degree of the valve section.
Miniaturization of such control valves may be required depending on equipment in which the control valves are installed. Despite the miniaturization, there may also be demands for a valve opening degree equivalent to those of conventional control valves so that a sufficient flow rate of a working fluid is ensured. There may also be demands for increasing the change in the valve opening degree (the change in the amount by which a valve element is lifted from a valve seat) with respect to the change in the pressure difference acting on a diaphragm regardless of the size of control valves.
In an attempt to address such demands, a technique of adjusting the corrugation pattern of a corrugated portion of a diaphragm and the height of the corrugation is proposed (refer, for example, to Japanese Patent Application Publication No. 2011-007355). Specifically, the corrugation pattern of a corrugated portion is adjusted so that the number of corrugations of the corrugation pattern has a fraction, such as one and a half corrugations. In addition, the height of corrugations above the circumference of the diaphragm is made equal to the height of the contact between the diaphragm and a disc. Such a structure increases the stroke of the diaphragm and thus increases the lift amount of the valve element as compared to conventional structures in which the number of corrugations has no fraction.